In general, a vehicle is equipped with a collision energy absorbing apparatus for absorbing shock force to protect passengers in the event of a car accident, for example, a crash.
In a vehicle such as a car, a train, or the like, moving at a high speed, a vehicle accident may occur due to a collision with another vehicle or a fixed structure. In this case, energy generated in the event of a vehicle accident needs to be effectively absorbed in order to secure passenger safety.
A method of absorbing collision energy according to the related art utilizes plastic energy generated when a collision structure member is deformed in the event of an accident. For example, a collision energy absorbing apparatus 10 may include a support part 10a provided with a fixture 1 and a plastic deformation part 10b provided in line with the support part 10a as shown in FIG. 1. In this configuration, as shown in FIG. 2, energy transferred from the colliding body 20 is converted into plastic energy generated as the plastic deformation part 10b is crushed, such that collision energy may be absorbed.
As such, since in the crush method used to absorb collision energy, all regions in structural members absorb collision energy, lightness thereof may be obtained.
However, since bending deformation may occur in a material and thus sufficient plastic deformation may not be provided therein, the energy absorption capability per unit mass of a member may be relatively low. Therefore, many attempts at increasing collision energy absorption capabilities through designing structural members having various shapes, for example, hexagonally-shaped collision structural members or the like, by adding a structure such as a foam member, a lattice rib, or the like, between structural materials, have been undertaken.
Meanwhile, in a case in which a length of a space available to absorb collision energy, based on vehicles type or structure, is relatively short, higher collision energy absorption capability per unit length is required.
For example, since, in a case of a train, a deformation space of a collision structural member at the time of a collision is relatively small, the maximum possible energy absorption capabilities of a material may be utilized by using a tube-expanding type collision energy absorbing apparatus. However, in this method, since a portion thereof, provided to expand a tube is a rigid body and so is not deformed, the weight of the apparatus may be heavy. This is the current situation with regard to difficulties in configuring an apparatus for wholly absorbing collision energy by using only plastic deformation utilizing tube-expansion.
As another example, unlike in the above-described case, an electrical car, a fuel-cell powered vehicle or the like, currently in development, may be relatively heavy and have relatively small amount of collision energy absorption space, therefore high collision energy absorption capability per unit length is required.
In this case, since the collision energy absorption method using the existing crush method has a small amount of plastic deformation from bending deformation, it is inappropriate to sufficiently utilize the high energy absorption capabilities of a high-elongation material and thus, a relatively large crush space is required.
In the case of a general collision, plastic deformation occurs through the bending deformation of a plate, and thus, a mean deformation rate may be approximately 20%. The surface of a plate excepting a center may undergo a large amount of deformation, while a central surface thereof may largely lack deformation. Thus, plastic deformation may be generated intensively only on a folded portion of the plate. Therefore, in terms of an overall collision member, the amount of plastic deformation may not be sufficient for the characteristics of a highly-elongated material.
Accordingly, the development of a collision energy absorption apparatus capable of absorbing a large amount of collision energy per unit length is necessary.